Curable organopolysiloxane compositions cure to form cured products having excellent heat resistance, cold resistance, electrical insulating properties, weather resistance, water repellency, and transparency, and therefore, the compositions are used in a wide range of industrial fields. In particular, cured products thereof are less likely to be discolored compared to other organic materials, and have reduced degradation of physical properties, and therefore are suitable as optical materials. For example, Patent Literature 1 proposes a liquid silicone resin composition for a light-emitting diode (LED) element, containing a silicone resin containing an alkenyl group, an organopolysiloxane containing a silicon-bonded hydrogen atom, and a catalyst for a hydrosilylation reaction.
Furthermore, the required performance of power semiconductors has been steadily increasing in recent years, and the required power density is in a difficult-to-achieve region with a conventional Si device. In these cases, higher power density is required, and a SiC power device is suggested as a device being developed in recent years. However, in order to achieve higher power density, driving must be possible even in high temperature conditions where the temperature of the chip surface during operation is 250° C. Therefore, there is strong demand for development of a sealing material that can withstand those temperatures and can maintain physical properties over a long period of time.
On the other hand, materials that are solid or semi-solid at room temperature have been proposed in recent years for new LED manufacturing processes. For example, Patent Literature 2 includes a sheet silicone resin composition for a light-emitting diode (LED), containing a silicone resin containing an alkenyl group, an organopolysiloxane containing a silicon-bonded hydrogen atom, and a catalyst for a hydrosilylation reaction; Patent Literature 3 includes a curable organopolysiloxane composition containing a solvent-soluble organopolysiloxane containing an alkenyl group, an organopolysiloxane containing a silicon-bonded hydrogen, and a catalyst for a hydrosilylation reaction, produced by a hydrosilylation reaction between the organopolysiloxane containing an alkenyl group and organopolysiloxane containing a silicon-bonded hydrogen atom; and Patent Literature 4 includes a silicone resin sheet formed by semi-curing a silicone resin composition containing an organopolysiloxane having at least two alkenylsilyl groups in one molecule, an organopolysiloxane having at least two hydrosilyl groups in one molecule, and a catalyst for a hydrosilylation reaction, and a reaction suppressant. However, the materials have problems where surface pressure-sensitive adhesion at 25° C. is provided, but hot melt properties are not sufficient, and thus is insufficient for practical applications. Furthermore, these materials have a problem where the hardness and physical strength are insufficient, and in particular, when exposed to a high temperature of 250° C. or higher, strength degradation is less likely to occur.
On the other hand, Patent Literature 5 proposes using both a hydrosilylation reaction catalyst and peroxide curing reaction in a heat curable composition containing an organopolysiloxane, but the composition is a pressure-sensitive adhesive, and there is no mention nor suggestion of a curable organopolysiloxane composition having hot melt properties. In particular, there is no mention nor suggestion of synthesizing an organopolysiloxane having a reactive functional group in advance by a curing reaction or semi-curing reaction.